currentGets a handle to the thread that invokes it.
current_idGets the unique identifier of the thread which invokes it.
current_or_unnamedGets a handle to the thread that invokes it. If the handle stored in thread-
local storage was already destroyed, this creates a new unnamed temporary
handle to allow thread parking in nearly all situations.
current_os_idGets the OS thread ID of the thread that invokes it, if available. If not, return the Rust
thread ID.
set_currentTries to set the thread handle for the current thread. Fails if a handle was
already set or if the thread ID of thread would change an already-set ID.
try_with_currentGets a reference to the handle of the thread that invokes it, if the handle
has been initialized.